Association between Lymph Node Ratio and Disease Specific Survival in Breast Cancer Patients with One or Two Positive Lymph Nodes Stratified by Different Local Treatment Modalities

PURPOSE Results of the American College of Surgeons Oncology Group (ACOSOG) Z0011 trial indicated that complete axillary node dissection (ALND) may not be warranted in some breast cancer patients with low tumor burden who are undergoing breast-conserving surgery following whole-breast irradiation. However, this study did not address patients undergoing mastectomy or those undergoing breast-conserving surgery without whole-breast radiotherapy. Given that lymph node ratio (LNR; ratio of positive lymph nodes to the total number removed) has been shown to be a prognostic factor in breast cancer, we first sought to determine the prognostic value of LNR in a low risk population comparable to that of the Z0011 trial and further to investigate whether the prognostic significance differs with local treatment modality. METHOD We used the Surveillance Epidemiology and End Results (SEER) database to identify breast cancer patients with T1-T2 tumor and 1-2 positive nodes. Patients were subclassified by the local therapy they underwent for the primary tumor. The prognostic value of LNR in predicting disease-specific survival (DSS) was examined in each treatment group. RESULTS A total of 53,109 patients were included. In the subgroup of 20,602 patients who underwent lumpectomy following radiotherapy, LNR was not found to be significantly associated with DSS in both the univariate and multivariate model. For the 4,664 patients treated with mastectomy following radiotherapy, 6,811 treated with lumpectomy without radiotherapy and 21,031 with mastectomy without radiotherapy, LNR independently predict DSS in each of these subgroups. CONCLUSIONS Our results add evidence to the concept that axillary dissection could be omitted in patients with one or two positive nodes following breast-conserving surgery and whole breast radiation.